Preparation method of exposure original plate

ABSTRACT

The preparation method of an exposure original plate according to the present invention includes a step of subdividing a pattern constituting an exposure original plate into a plurality of rectangular patterns, a step of extracting micro patterns having the size of a side smaller than a prescribed value from among the divided individual rectangular patterns, a step of forming a corrected micro pattern by increasing the size of the side of the extracted micro pattern perpendicular to the side making contact with an adjacent patter at least by the prescribed value, a step of forming a corrected adjacent pattern by retreating the side of the adjacent pattern making contact with the corrected micro pattern by the increased amount corresponding to the prescribed value, and a step of finding EB exposure data for the pattern including the corrected micro pattern and the corrected adjacent pattern, and carrying out EB exposure by the variable shaped beam exposure method based on the EB exposure data.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a preparation method of an exposureoriginal plate such as a photo mask and a reticle, and more particularlyto a preparation method of forming a required pattern on the originalplate by means of an electron beam (referred to as EB hereinafter)exposure.

2. Description of the Prior Art

The preparation of an exposure original plate such as a photo mask and areticle by the EB exposure technology is accomplished by irradiating anEB sensitive resist formed on a transparent substrate with EBs in arequired pattern using an EB exposure system. In the irradiation of EBsin the required pattern, there exists a technology of scanning the EBsensitive resist with one or a plurality of EBs, or a technology ofirradiating the EB sensitive resist with an EB or EBs with its crosssection formed in a rectangular form. In either case, it is necessary toprepare exposure data corresponding to a desired pattern to be formed,and carry out EB scanning or exposure using the EB exposure system basedon the exposure data.

In the preparation of the EB exposure data, the pattern of the exposureoriginal plate is subdivided into a plurality of rectangular patterns,and data processing is executed by recognizing individual dividedrectangular patterns. In the data processing, the so-called opticalproximity effect correction (OPC), which corrects the pattern for eachpart by taking the optical proximity effect into account, is employed,where a technique of a bias method or an inner serif method isavailable. These are technologies which correct parts of the shape of anobject pattern by finding the correlations between the shapes ofadjacent patterns, the dimensions between the patterns, and the like.For example, in the bias method, when proximity patterns P2 and P3 existin parts of a linear wiring pattern P1, as shown in FIG. 14A, a wiringpattern in which part of each side of the wiring pattern P1 is deletedto reduce the pattern width according to the OPC as shown in FIG. 14B,is prepared in order to prevent short-circuiting between these patternsin the pattern formed on the exposure original plate, and EB exposuredata corresponding to the corrected pattern are generated. In themeantime, in the inner serif method, when a gate electrode pattern P4for a MOS transistor is bent in U-shape on both sides of a source-drainregion SD, for example, as shown in FIG. 15A, in order to prevent anincrease in the gate electrode dimension (gate electrode length) asshown by a broken line in the figure in the connection parts between thebent patterns P42, P43 on both sides and the central rectangular patternP41, gate electrode pattern in which the inner side of the connectionpart is deleted to reduce the gate electrode length of the connectionpart, is created as shown in FIG. 15B, and EB exposure datacorresponding to the corrected pattern are prepared.

However, with such a pattern correction by OPC, a problem arises in thatmicro patterns are generated when the corrected pattern is divided intorectangular patterns. Namely, in the case of the wiring pattern P1 inwhich portions located close to the proximity patterns are partiallyremoved by the bias method as shown in FIG. 14B, division into aplurality of rectangular patterns P10, P11 and P12 as shown in FIG. 14Cgenerates a rectangular pattern P10 with extremely small width directionsize in the portion left by the removal, which becomes a micro pattern.In addition, in the case of the gate electrode pattern P4 by whichU-shaped bent part is removed by the inner serif method as shown in FIG.15B, rectangular patterns P44, P45 and P46 with extremely small size inrespective width directions are generated in the regions across theremoved portions as shown in FIG. 15C, which become micro patterns.

In recognizing the divided individual rectangular patterns, EB exposuredata are prepared by regarding even such a micro pattern, recognized asa micro pattern, as an independent pattern, and EB exposure is carriedout based on the obtained EB exposure data. In this case, in the EBexposure method using the point beam raster scan method which EB exposesa required pattern while continuously scanning a mask original platewith an EB of minute beam diameter among EB exposure methods, since thediameter of the EB beam can be reduced to about 0.08 μm, it is possibleto expose properly a minute pattern of 0.1 μm. However, since a graphicis deleted in the units of about 0.004 μm in the bias method, roundingin the exposed image occurs at the minimum grid of the diameter of theEB beam. Accordingly, the point beam raster scan method is notapplicable to the bias method.

In the meantime, when the exposure method using the variable shaped beamvector scan system (referred to as variable shaped beam exposure methodhereinafter) is employed as the EB exposure method, since the currentminimum grid is 0.002 μm, the problem of rounding will not occur, butthere may arise a case in which it is not possible to EB expose a micropattern as a normal pattern. The variable shaped beam exposure method isa technology in which EB beams are formed into a rectangular beam ofrequired size by an aperture, further reducing it to an EB of beambundle with a minute rectangle by a reduction lens, and expose anexposure original plate with the reduced EB. Because of this, assumingthat beam blur due to optical proximity effect in the periphery of therectangular bundle of EB is generated at a width of, for example, about0.1 μm, the effect of the optical proximity effect on the pattern isinevitable when the size of at least one of the sides of the micropattern is less than 0.1 μm, and it becomes impossible to normallyexpose a micro pattern. As a result, pattern defects arise in a patternof prepared exposure original plate, and if a semiconductor device ismanufactured using an exposure original plate with such pattern defects,abnormality in the characteristics of the semiconductor device willoccur.

For example, when the pattern is divided into rectangular patterns as inFIG. 14C, the micro pattern P1O fails to be exposed normally as shown inFIG. 14D, with the wiring width of the wiring pattern P1 becoming thinat the intermediate part, the wiring resistance is increased or thewiring is disconnected. In the case of the gate pattern P4 in FIG. 15 B,the micro patterns P44, P45 and P46 generated by the division as shownin FIG. 15C fail to be exposed properly, and a gate electrode is formedwith the width size, namely the gate electrode length, being especiallysmall in the pattern P41, as shown in FIG. 15D. Accordingly, when micropatterns are generated in the execution of the bias method or the innerserif method, in order to preclude anomalies in the characteristics ofthe semiconductor device caused by such pattern defects in the exposureoriginal plate, it has been conventional to withdraw the correctionportions of the pattern so as to eliminate the micro patterns and tointroduce a processing for reinstating the original pattern. As aresult, effective use of the bias method or the inner serif methodfailed, and in that sense elimination of the drawback in the exposureoriginal plate could not be realized.

In Japanese Patent Applications Laid Open, No. 2000-323389 is discloseda technique, when EB exposure is executed in divided manner, ofdesigning pattern data so as to provide a region where two patterns canbe overlapped in a plane, in order to prevent generation of patterndiscontinuity in the connection part. However, since this technique isapplicable only to a connection part of the patterns and does not applyto micro patterns which do not involve connection with another pattern,such as the micro pattern generated in a part of the pattern by the OPCby the inner serif method as shown in FIG. 15, and is unable toeliminate a drawback due to such a micro pattern.

Moreover, Japanese Patent Applications Laid Open, No. Hei 9-129531discloses a technique of taking the direction of the pattern divisioninto consideration so as not to generate micro patterns in dividing apattern into rectangular patterns. Since, however, patterns corrected bythe bias method or the inner serif method tend to generate fineirregularities, it is not necessarily possible to prevent the generationof the micro patterns. For example, when the OPC due to the bias methodis applied to the edges on the mutually opposite sides, to a linearwiring pattern as shown in FIG. 14, it is inevitable to generate micropatterns in dividing the wiring pattern in either one of longitudinal orlateral direction using the technique described in this disclosure, andit is difficult to eliminate the problem in the above.

BRIEF SUMMARY OF THE INVENTION

Summary of the Invention

The preparation method of an exposure original plate according to thepresent invention includes a step of dividing a pattern constituting theexposure original plate into a plurality of rectangular patterns, a stepof extracting micro patterns having the size of a side smaller than aprescribed value from among the divided individual rectangular patterns,a step of forming a corrected micro pattern for the extracted micropattern in which the size of at least the side perpendicular to a sidein contact with an adjacent pattern is increased by a prescribed amount,a step of forming a corrected adjacent pattern by retreating the side ofthe adjacent pattern which has been in contact with the side of thecorrected micro pattern by the increased portion of the prescribedamount, and a step of finding EB exposure data for the pattern includingthe corrected micro patterns and the corrected adjacent patterns, andexecuting EB exposure by the variable shaped beam exposure method basedon the EB exposure data.

BRIEF DESCRIPTION OF THE DRAWINGS

The above-mentioned and other features and advantages of this inventionwill become more apparent by reference to the following detaileddescription of the invention taken in conjunction with the accompanyingdrawings, wherein:

FIG. 1 is a flowchart of a first embodiment of the preparation methodaccording to the present invention;

FIGS. 2A to 2E are respectively pattern diagrams showing specificexamples of the processing of the first embodiment;

FIG. 3 is a conceptual configuration diagram of a variable shaped beamexposure system;

FIG. 4 is a flowchart of a second embodiment of the preparation methodaccording to the invention;

FIGS. 5A to 5E are respectively pattern diagrams showing specificexample of the processing of the second embodiment;

FIG. 6 is a flowchart of a third embodiment of the preparation methodaccording to the invention;

FIGS. 7A to 7C are respectively part 1 of pattern diagrams showingspecific examples of the processing of the third embodiment;

FIGS. 8A to 8D are respectively part 2 of pattern diagrams showingspecific examples of the processing of the third embodiment;

FIG. 9 is a flowchart of a fourth embodiment of the preparation methodaccording to the invention;

FIGS. 10A to 10E are respectively pattern diagrams showing specificexamples of the processing of the fourth embodiment;

FIG. 11 is a flow chart of a fifth embodiment of the preparation methodaccording to the invention;

FIGS. 12A to 12C are respectively part 1 of pattern diagrams showingspecific examples of the processing of the fifth embodiment;

FIGS. 13A to 13D are respectively part 2 of pattern diagrams showingspecific examples of the processing of the fifth embodiment;

FIGS. 14A to 14D are respectively pattern diagrams for showing the OPCby the conventional bias method and its problems; and

FIGS. 15A to 15D are respectively pattern diagrams for showing the OPCby the conventional inner serif method and its problems.

DETAILED DESCRIPTION OF THE INVENTION

Referring to the drawings, the embodiments of the present invention willbe described. FIG. 1 is a flowchart for a first embodiment. First, anOPC according to the bias method or the inner serif method is applied tomask data (S101). Then, the pattern obtained by the OPC is subdividedinto a plurality of rectangular patterns (S102). Next, the size of eachside is detected for each divided rectangular pattern (S103), and arectangular pattern with the smallest size of the side less than aprescribed size (0.1 μm here) is extracted as a micro pattern (S104).When a micro pattern is not extracted, it proceeds to S110 to bedescribed later. When a micro pattern is extracted, it is determined forthe micro pattern whether the long side to which the adjacent pattern isin contact in the short side direction exists on only one side edge (theword an edge being used for a side as deemed appropriate) or on bothside edges (S105). Here, what is described by being in contact with oneside edge means that the micro pattern is making contact on one edgewith an adjacent pattern on one side, and being in contact with bothside edges means that the micro pattern is making contact with adjacentpatterns on both sides.

Next, the micro pattern is subjected to a thickening processing in thewidth direction with respect to the long side making contact with theadjacent pattern, to create a corrected micro pattern having a size ofthe short side not less than 0.1 μm, preferably larger than 0.2 μm. Inthis case, when there is involved one side edge of the micro pattern,thickening is performed only for the long edge on one side of the micropattern (S106), and when there are involved both side edges, thickeningis performed for both of the long edges (S107). Next, the side of thepattern adjacent to the long side of the micro pattern subjected to thethickening is retreated by deleting the portion corresponding to thethickened width (S108). The above processing is applied to all the micropatterns to create corrected patterns subjected to thickening processingfor the micro patterns, and to form a corrected adjacent patternsubjected to the side retreat processing for the adjacent pattern(S109). Then, EB exposure data are prepared based on the corrected micropatterns, the corrected adjacent pattern and the other patterns notsubjected to correction (S110), and an EB exposure is executed by thevariable shaped beam method according to the EB exposure data (S111).

FIG. 2 is a drawing showing a specific example of the pattern of thefirst embodiment corresponding to the pattern shown in FIG. 14. Assumethat there exist a linear wiring pattern P1 with a prescribed width, andproximity patterns P2 and P3 that are in close proximity to the patternP1, as shown in FIG. 2A. As a result of execution of an OPC according tothe bias method, the sides opposite to the proximity patterns P2 and P3of the wiring pattern P1 are deleted at different positions of thesides, and there is generated a crank-shaped portion X1 in a part in thelength direction of the wiring pattern P1 as shown in FIG. 2B. When thepattern obtained by the OPC is divided into rectangular patterns, arectangular pattern P10 with a micro width is generated at thecrank-shaped portion X1 between rectangular patterns P11 and P12extending on both sides in the length direction. Since a rectangularpattern with the lateral size (the up and down direction and the leftand right direction of the drawings will be referred to as longitudinaland lateral directions hereinafter) less than 0.1 μm is defined as amicro pattern here, the rectangular pattern P10 will be extracted as amicro pattern because the lateral size of the rectangular pattern P10with micro width will be assumed to be less than 0.1 μm.

Since the micro pattern P10 makes contact with the adjacent rectangularpatterns P11 and P12 at edges on both sides, the micro pattern P10 issubjected to a thickening processing for edges on both sides to expandthe edges on both sides of the micro pattern P10 toward the outside by0.1 μm each, obtaining a corrected micro pattern 10C with the totallateral size of 0.3 μm. In addition, corresponding to the thickeningprocessing of the micro pattern P10, the corresponding sides of theadjacent rectangular patterns P11 and P12 on both sides are retreated bydeleting portions of width of 0.1 μm to form corrected adjacent patternsP11C and P12C. Then, EB exposure data for the corrected micro patternP10C and the corrected adjacent patterns P11C and P12C thus formed areprepared, and by carrying out exposure using a variable shaped beamexposure system based on the EB exposure data, wiring pattern P1C is EBexposed in a pattern as shown in FIG. 2E.

FIG. 3 is a schematic block diagram of a variable shaped beam exposuresystem. Electron beams emitted from an electron gun 11 are converged byan irradiation lens 12, Ebs passing through a first aperture 13 aredeflected and condensed by a shaping and deflecting unit 14 and ashaping lens 15, and the beams are formed into a desired rectangularbeam bundle by a second aperture 16. The bundle is reduced to a microrectangular beam bundle by a reduction lens 17, and the beam isprojected by a projection lens 18 and a deflector 19 onto a desired siteof an exposure original plate 21, which will serve as a photo mask,placed on a stage 20. Here, the shaping and deflecting unit 14 and theshaping lens 15 are controlled based on the EB exposure data set in acontrol section 10, and an EB beam with a rectangular patterncorresponding to the EB exposure data is formed. Then, in cooperationwith the XY movement of the stage 20, exposure in step and repeatfashion is carried out sequentially to the exposure original plate 21.Since beam blurring due to the optical proximity effect in the vicinityof the rectangular beam occurs with a width of about 0.1 μm in thisvariable shaped beam exposure system, the influence on the drawn patterndue to the optical proximity effect becomes inevitable when the size ofthe short side of the micro pattern is less than 0.1 μm, so that normalexposure of a micro pattern becomes impossible as mentioned above.

However, since the rectangular pattern of the micro pattern with a sizesmaller than 0.1 μm is subjected to a thickening processing to change itto a rectangular pattern of the corrected micro pattern with a sidelarger than 0.1 μm (here, it is larger than 0.2 μm), it is possible toeliminate the influence of the optical proximity effect by EB exposingthe corrected micro pattern P10C and the corrected adjacent patternsP11C and P12C as shown in FIG. 2D by using such a variable shaped beamexposure system. Accordingly, when a corrected micro pattern and anadjacent, corrected adjacent pattern are exposed sequentially, it ispossible to form a pattern which is in proper continuation of bothpatterns, and it is possible to prevent a pattern defect at theconnection portion of the patterns.

FIG. 4 is a flowchart for a second embodiment of the invention. Similarto the first embodiment, an OPC by the bias method or the inner serifmethod is applied to mask data (S201). Next, the pattern obtained by theOPC is subdivided into a plurality of rectangular patterns (S202). Next,the size of the sides in the longitudinal and the lateral directions ofeach divided rectangular pattern is measured (S203), and rectangularpatterns having a prescribed size (here, it is less than 0.1 μm) on bothof the longitudinal and the lateral sides are extracted as both-edgemicro patterns (S204). If a both-edge micro pattern is not extracted, itis moved to the processing in step S104 of the flowchart shown in FIG. 1in the first embodiment, and micro patterns are extracted.

When both-edge micro patterns are extracted, it is determined if[L11−(Lh+0.11)]≦0 and/or [L12−(Lh+0.11)]≦0 is satisfied. Here, Lh is thewidth size of the both-edge micro pattern (length size is represented byLw), and L11 and L12 are respectively the width sizes of the adjacentpatterns that make contact with the both-edge micro pattern in thelength direction. For example, referring to FIG. 5C or FIG. 7A of theembodiments to be described later, the width sizes of the adjacentpatterns P11 and P12 are represented by L11 and L12, and the width sizeof the both-edge micro pattern P13, sandwiched by these adjacentpatterns, is represented by Lh. By subtracting the sum of the width sizeLh of the both-edge micro pattern and 0.11 from L11 and L12 it can bedetermined that the adjacent patterns are not micro patterns. When atleast one of the above inequalities is satisfied, the processing movesto step S300 of FIG. 6 described later (S205). When the conditions arenot satisfied, for the extracted both-edge micro pattern, a thickeningprocessing is carried out in the longitudinal and the lateral directionsfor each side, without detecting presence or absence of the adjacentpatterns, to create a corrected both-edge micro pattern having the sizeof each side larger than 0.1 μm, preferably larger than 0.2 μm (S206).Next, when there exists a pattern adjacent to the corrected both-edgemicro pattern, corresponding to the thickening processing of theboth-edge micro pattern, the common side of the adjacent pattern and themicro pattern is subtracted and retreated by the width of 0.1 μm fromthe adjacent patterns, and for the retreated side, rectangular divisionof inserting a cut in the short side direction of the adjacent patternis applied to obtain a corrected adjacent pattern (S207). Thisprocessing is applied to all the both-edge micro patterns to create acorrected both-edge micro patterns (S208). Then, EB exposure data areprepared based on the corrected both-edge micro patterns, correctedadjacent patterns and the other patterns (S209), and EB exposure isexecuted by the variable shaped beam method using the EB exposure data.

FIG. 5 is a drawing showing a specific example of the pattern of asecond embodiment. This is an example in which an OPC by the bias methodis applied to a part of both sides of a linear wiring pattern P1 similarto that in the first embodiment as shown in FIG. 5A, and a thin widthpart X5 is generated in a part in the length direction of the wiringpattern as shown in FIG. 5B. When the pattern subjected to the OPC issubdivided into rectangular patterns, there is created a rectangularpattern P13 with small longitudinal and lateral sizes in the thin widthpart X5 as shown in FIG. 5C. When the longitudinal size Lh and thelateral size Lw are both less than 0.1 μm, the rectangular pattern P13is extracted as a both-edge micro pattern. Next, for the both-edge micropattern P13, the determination in step S205 in FIG. 4 is applied basedon its relation with the width sizes L11 and L12 of the adjacentpatterns P11 and P12. Since the conditions of step S205 are notsatisfied in this case, all the sides of the both-edge micro pattern P13are subjected to the thickening processing, each side of the both-edgemicro pattern P13 is increased by 0.1 μm, as in FIG. 5D, to form acorrected both-edge micro pattern P13C with each of the longitudinal andlateral sides of a total of about 0.2 μm. Next, corresponding to thethickening processing of the micro pattern P13, the corresponding commonsides, with P13, of the adjacent patterns P11 and P12 on both sides areretreated by a width of 0.1 μm respectively, to form corrected adjacentpatterns P11C and P12C. Electron beam exposure data for the correctedboth-edge micro pattern P13C and the corrected adjacent patterns P11Cand P12C thus formed are prepared, and by carrying out exposure usingthe variable shaped beam exposure system based on the EB exposure data,EB exposure of pattern of FIG. 5E is executed.

In this way, since a corrected both-edge micro pattern having arectangular pattern with longitudinal and lateral sizes less than 0.1 μmis changed here to a rectangular pattern with longitudinal and lateralsizes of about 0.2 μm by subjecting it to a thickening processing ofmore than 0.1 μm, so that it is possible to eliminate the influence ofthe optical proximity effect on the drawing pattern. Accordingly, whenthe corrected both-edge micro pattern and its adjacent pattern areexposed sequentially, it is possible to form a pattern in which bothpatterns are in properly continuous state, and a pattern defect at theconnection portion can be prevented. At the same time, no EB exposuredefect will be generated in the micro pattern in the directionperpendicular to the side which is making contact with the adjacentpattern, so that defect such as disconnection of a linear wiring can beprevented.

In the second embodiment, the processing of step S207, namely, theprocessing of retreating the common side which is making contact withthe corrected both-edge micro pattern, of the adjacent pattern makingcontact with the corrected both-edge micro pattern, may be omitted, orthe portion subjected to the thickening processing where the correctedboth-edge micro pattern and the adjacent pattern are making contact maybe subjected to a double exposure. No special problem will occur in theprepared pattern by such a modification. Moreover, since the adjacentpattern is not given a processing of retreating its side correspondingto the corrected both-edge micro pattern, it is possible to reduce theprocessing man-hours and shorten the processing time.

Next, a modification in the processing of retreating the adjacentpattern, in the second embodiment, will be described as a thirdembodiment. Since the adjacent patterns P11 and P12 in FIG. 5D aresubjected to a retreat processing in the second embodiment, there mayoccur a case in which the corners of the corrected both-edge micropattern P13C are left behind. Then, a processing for correcting such asituation becomes necessary. A flowchart S300 for this purpose is shownin FIG. 6. When a both-edge micro pattern is detected in step S204 inFIG. 4 of the second embodiment, and the relations in step S205 aresatisfied between the both-edge micro pattern and the adjacent patternsP11 and P12, in other words, when the longitudinal and lateral sizes aremeasured for the sides of a pattern to be the basis for the obtained newrectangular pattern, it is determined whether a side which becomes asthe basis for a new micro pattern exists or not, and if there is foundthe existence of a side to be the basis for a new micro pattern, theprocessing flow moves to step S300 of the third embodiment, as mentionedabove.

In the meantime, when the existence of a side that becomes the basis forthe new micro pattern is found in step S205, the adjacent pattern issubjected to a thickening processing along the side of the micro patternfor the side where a new rectangular pattern is generated, to create afirst thickened pattern (S301). In addition, the edge on the side wherethe new rectangular pattern is created, among the four sides of themicro pattern, is subjected to a thickening processing to the regionincluding the new rectangular pattern, to create a second thickenedpattern (S302). After that, the common thickened pattern is extracted bytaking the logical product of (ANDing) the first thickened pattern andthe second thickened pattern (S303), and a micro pattern is creatednewly by unifying the result of the logical product and the old micropattern (S304). Thereafter, the processing returns to step S104 of thesecond embodiment, creates a corrected one-edge micro pattern for asecond time, and the processing continues to EB exposure.

FIG. 7 is a drawing showing a specific example of the pattern of a thirdembodiment. After division processing into rectangular patterns, andcreation of a both-edge micro pattern P13 and adjacent patterns P11 andP12 as shown in FIG. 7A, a corrected both-edge micro pattern P13C isformed by subjecting the both-edge micro pattern P13 as shown in FIG.7B. By carrying out division into rectangles by removing the overlappingportions P11 x and P12 x of the adjacent patterns P11 and P12 with thecorrected both-edge micro pattern P13C from the adjacent patterns P11and P12, there are generated new rectangular patterns P11A and P12A ofnew extended shape. When the longitudinal size of the adjacent patternsP11 and P12 are called L11 and L12, and the longitudinal and lateralsizes of the both-edge micro pattern P13 are called Lh and Lw, since thelongitudinal and lateral sizes of the corrected both-edge micro patternP13C when it is subjected to a thickening processing of 0.11 μm are(Lh+0.11 μm) and (Lw+0.11 μm), respectively, the longitudinal sizes ofthe new rectangular patterns P11A and P12A are given by [L11−(Lh+0.11)]and [L12−(Lh+0.11)], respectively. Accordingly, if these longitudinalsizes are larger than 0.1 μm, the new rectangular patterns are notclassified as micro patterns, and EB exposure is possible by treatingthem as independent rectangular patterns.

In the meantime, if the longitudinal sizes [L11−(Lh+0.11)] and[L12−(Lh+0.11)] of the new rectangular patterns P11A and P12A arerespectively smaller than 0.1 μm, the new rectangular patterns P11A andP12A are classified as micro patterns. For this reason, the thickeningprocessing for the both-edge micro pattern P13 is withdrawn and theprocessing is returned to the state in FIG. 7A. Then, the adjacentpatterns P11 and P12 are subjected to a thickening processing of 0.11 μmalong the lateral side direction of the both-edge micro pattern P13, fortheir longitudinal sides making contact with, but not overlapping with,the both-edge micro pattern P13, to create first thickened patterns P11a and P12 a as shown in FIG. 8B. In addition, separately from the above,a thickening processing is executed for the both-edge micro pattern P13only in the longitudinal direction as shown in FIG. 8C. In thethickening processing, in order to have [L11−(Lh+0.11)] and[L12−(Lh+0.11)] to be larger than 0.1 μm, the longitudinal size of theboth-edge micro pattern P13 is extended to the above and below,respectively, in the longitudinal direction by 0.2 μm, to create secondthickened patterns P13 a and P13 b. After that, logical product betweenthe first thickened patterns P11 a, P12 a and the second thickenedpatterns P13 a and P13 b are taken, and common thickened patterns P13Aand P13B are obtained as shown in FIG. 8D. Then, the common thickenedpatterns P13A and P13B are unified with the both-edge micro pattern P13,a corrected one-edge micro pattern is created for the obtained one-edgemicro pattern (P13 +P13A +P13B) for a second time, and EB exposure isexecuted with the obtained result treated as an independent rectangularpattern thereafter. According to the third embodiment, missing of thepattern at the corners of the corrected both-edge micro pattern P13Cthat occurred in the second embodiment can be prevented, and moresatisfactory pattern exposure becomes possible. Although description isgiven in FIG. 8 assuming that both of the new rectangular patterns P11Aand P12A are micro patterns, the thickening processing is required onlyfor one pattern alone if only one of them is a micro pattern.

FIG. 9 is a flowchart of a fourth embodiment of the invention. Analogousto the first embodiment, an OPC according to the bias method or theinner serif method is applied to mask data (S401). Next, the patternobtained by the OPC is subdivided into a plurality of rectangularpatterns (402). Then, the size of respective sides is detected for eachof the divided rectangular pattern (S403), and rectangular patternshaving the size of the shortest length less than a prescribed value(here it is 0.1 μm) are extracted as micro patterns (S404). When a micropattern is not detected, processing is moved to step S410 to bedescribed later. When a micro pattern is extracted, it is determined forthe micro pattern whether the long edge that makes contact with anadjacent pattern in the direction of the short edge occurs on one sideedge or occur on both side edges (S405). What is meant by the case ofone side edge is the case in which the micro pattern is in contact withthe edge of an adjacent pattern on only one side, and the case of bothside edges means that the micro pattern makes contact with adjacentpatterns on both sides.

Next, the micro pattern is subjected to a thickening processing of morethan 0.1 μm in the width direction for the long side making contact withan adjacent pattern, to create a corrected micro pattern having the sizeof a short side preferably longer than 0.2 μm. In this case, thickeningprocessing is carried out for only one long edge on one side of themicro pattern for the case of one side edge (S406), and thickeningprocessing is carried out for both long edges in the case of both sideedges (407). A corrected micro pattern is formed after repeating theabove processing for all the micro patterns (S409). After that, EBexposure data are prepared based on the corrected micro pattern and theother pasterns including adjacent patterns (S410), and EB exposure isexecuted by the variable shaped beam method using the EB exposure data(S311).

FIG. 10 is a drawing showing a specific example, corresponding to theexample shown in FIG. 15, of the pattern according to a fourthembodiment. Here, an OPC by the inner serif method is applied to aU-shaped gate electrode pattern P4, and protrusions X2, X3 and X4 aregenerated on the inner face side of respective sides P41, P42 and P43 asshown in FIG. 10A. By dividing the pattern into rectangular patterns,rectangular patterns P44, P45 and P46 with micro width are created inprotrusions X2, X3 and X4, respectively, as shown in FIG. 10B. Since thewidth sizes of the rectangular patterns P44, P45 and P46 are assumed tobe less than 0.1 μm here, the rectangular patterns P44, P45 and P46 areextracted as micro patterns. Next, from the connection conditions of themicro patterns P44, P45 and P46 with the adjacent patterns P41, P42 andP43, since the micro patterns P44, P45 and P46 make contact with theadjacent rectangular patterns P41, P42 and P43 only on one side edge,thickening processing is executed for the one side edges of the micropatterns P44, P45 and P46 that are making contact, increasing the widthof the edges on one side of each micro pattern by 0.1 μm, formingcorrected micro patterns P44C, P45C and P46C with a total width size ofabout 0.2 μm. Then, EB exposure data are prepared for the correctedmicro patterns P44C, P45C and P46C thus obtained, and the adjacentpatterns P41, P42 and P43, and a gate electrode pattern P4C as shown inFIG. 10D is obtained by EB exposure by carrying out exposure using thevariable shaped beam exposure system based on the EB exposure data.

Since the rectangular pattern with size of less than 0.1 μm of the micropattern is subjected to thickening processing of more than 0.1 μm toform a rectangular pattern of more than 0.2 μm here, it is possible toeliminate the influence of the optical proximity effect on the drawnpattern. Accordingly, when the corrected micro pattern and the correctedadjacent pattern making contact with it are exposed sequentially, it ispossible to form a pattern in which both patterns are in a properlycontinuous condition, so that generation of pattern defects at theconnection portion of the patterns can be prevented. Here, it is to benoted in this embodiment that the corrected micro pattern overlaps withthe adjacent pattern in the portions where its width is increased, sothat the so-called double exposure takes place there, but no specialproblem will arise in the prepared pattern. Moreover, since theprocessing of retreating the side of the adjacent pattern correspondingto the corrected micro pattern is not applied in this embodiment, it ispossible to reduce the processing man-hours and shorten the processingtime compared with the first embodiment.

FIG. 11 is a flowchart of a fifth embodiment in which retreat processingis applied to the adjacent patterns in the fourth embodiment. Analogousto the fourth embodiment, an optical proximity effect correctionprocessing S501, a rectangular pattern division S502, a size measurementof sides of divided rectangular patterns S503 and a micro patterndetection S504 are carried out. When no micro pattern is detected, theprocessing moves to step S410 of the fourth embodiment shown in FIG. 9.When some of the divided rectangular pattern are detected as micropatterns, the size of the smallest side E22 of all sides of the newrectangular patterns, except for the above micro patterns, is measuredto determine whether it is less than 0.1 μm or not (S505). If the sizeof the side E22 is larger than 0.1 μm, since new micro patterns will notbe generated from the newly divided rectangular patterns, a thickeningprocessing is applied to the one side edge of the micro pattern (S506),and the adjacent pattern is subjected to a retreat processingcorresponding to the amount of the thickening (S507). Processing fromstep S505 is repeated until it is applied to all the micro patterns(S508), and thereafter, preparation of EB exposure data (S509) and EBexposure (S510) are executed.

On the other hand, when it is found in step S505 that the size of theside E22 of the new rectangular pattern is less than 0.1 μm, the newrectangular pattern found to be a micro pattern is subjected to athickening processing in the length direction of the new micro patternto form a first thickened pattern (S511). In addition, a thickeningprocessing is applied to the micro pattern along the side E22 of the newrectangular pattern that is determined to be a new micro pattern to forma second thickened pattern (S512). Then, logical product between thefirst thickened pattern and the second thickened pattern is taken toobtain the common thickened pattern (S513). After that, a new micropattern is created by unifying the common thickened pattern and themicro pattern (S514) Accordingly, since the new micro pattern includes arectangular pattern generated in step S502, the processing moves to stepS406 of the fourth embodiment, and a corrected micro pattern is formedfor a second time.

FIG. 12 is a drawing showing a specific example of the pattern of thefifth embodiment. Here, it is showing an example in which an OPCaccording to the bias method is applied to a linear wiring pattern P21,and a micro pattern P22 is generated on one side of the wiring patternwhen it is subdivided into rectangular patterns. The generated micropattern P22 is subjected to a thickening processing with respect to oneside edge of the adjacent pattern P21 to form a corrected micro patternP22C Then, the overlapped portion of the adjacent pattern P21 and thecorrected micro pattern P22C is deleted from the adjacent pattern P21,and when the remaining adjacent pattern P21 is divided into rectangles,new rectangular patterns P21A and P21B are formed in parts of theadjacent pattern P21 as shown in FIG. 12B. The size of the smallest sideE22 of the new rectangular patterns P21A and P21B formed newly ismeasured. If it is larger than 0.1 μm, it is not classified as a micropattern, and its exposure becomes possible. In the case of FIG. 12C,neither of the new rectangular patterns P21A and P21B is classified as amicro pattern, and hence, the corrected micro pattern P22C and the newrectangular patterns P21A and P21B can be EB exposed as independentrectangular patterns.

On the other hand, when the size of the side E22 of the new rectangularpattern is less than 0.1 μm, either one of these new rectangularpatterns will become a micro pattern. FIG. 13A shows an example in whichthe new rectangular pattern P21B is generated as a micro pattern. Undersuch a condition, division into rectangles is withdrawn, and athickening processing is applied along the lateral side of the micropattern P22 as shown in FIG. 13B, with respect to the side E22 of thenew rectangular pattern P21B recognized as a micro pattern in FIG. 13A,to form a first thickened pattern P21 a. In addition, as for the micropattern P22, a thickening processing is carried out along the side E22of the new rectangular pattern P21B to generate a second thickenedpattern P22 a as shown in FIG. 13C. Then, the logical product of thefirst thickened pattern P21 a and the second thickened pattern P22 a istaken, to obtain the common thickened pattern P22A as shown in FIG. 13D.The common thickened pattern P22A is unified with the micro pattern P22,and a thickening processing is executed using a new micro pattern(P22+P22A) to generate a corrected micro pattern, and EB exposure isexecuted. According to the fifth embodiment, when rectangular patternsare generated anew in the adjacent pattern in the generation of thecorrected micro pattern, it is possible to prevent new generation ofmicro patterns.

The embodiments in the above are examples of the present invention, andneedless to say, specific examples of the patterns to which the presentinvention is applicable are not limited to the first to the thirdembodiments. For example, the manufacturing method of the secondembodiment is applicable to the pattern described in the firstembodiment, and conversely, the manufacturing method described in thefirst embodiment is applicable to the pattern described in the secondembodiment. Moreover, although the embodiments are described inconjunction with examples in which the influence of the opticalproximity effect in the EB exposure system appears for a size of 0.1 μm,when an original plate for exposure is prepared using an EB exposuresystem in which the influence of the optical proximity effect appears ata larger or a smaller value than 0.1 μm, what one is required to do isto simply modify the relevant size in respective embodiments.

As described in the above, according to the present invention, individing a pattern into rectangular patterns and EB exposing the dividedrectangular patterns onto an exposure original plate by using a variableshaped beam exposure system, through extraction of micro patterns, andsubjecting the micro patterns to a thickening processing by which theminimum size of the extracted micro patterns is changed to a size largerthan a size for which the influence of the optical proximity effect doesnot appear, the influence of the optical proximity effect on the exposedpattern in EB exposure of each rectangular pattern by the variableshaped beam exposure system is eliminated, and makes it possible to forma normal pattern on an exposure original plate by proper EB exposure ofthe micro patterns. In this way, when an exposure original plate isprepared by EB exposure of the pattern obtained by the OPC, it ispossible to prevent pattern defect in the prepared exposure originalplates and prevent generation of abnormality in the characteristics ofsemiconductor devices manufactured by using the exposure original plate.

Although the invention has been described with reference to specificembodiments, this description is not meant to be construed in a limitedsense. Various modifications of the disclosed embodiments will becomeapparent to persons skilled in the art upon reference to the descriptionof the invention. It is therefore contemplated that the appended claimswill cover any modifications or embodiments as fall within the truescope of the invention.

1. A preparation method of an exposure original plate, comprising:subdividing a pattern constituting an exposure original plate into aplurality of rectangular patterns; extracting at least one micro patternhaving a side with a size smaller than a prescribed value from among theplurality of rectangular patterns; forming a corrected micro pattern forthe extracted micro pattern in which a size of a side of the extractedmicro pattern perpendicular to another side of the extracted micropattern making contact with an adjacent pattern is increased by at leastthe prescribed value; correcting the adjacent pattern, to form acorrected adjacent pattern, by retreating the side of the adjacentpattern which has been in contact with said corrected micro pattern bysaid prescribed amount of increase; finding Electron Beam (EB) exposuredata for a pattern including said corrected micro pattern and saidcorrected adjacent pattern, and carrying out EB exposure by the variableshaped exposure system based on the EB exposure data.
 2. The preparationmethod of an exposure original plate as claimed in claim 1, furthercomprising: determining whether or not there exists a side of one of atleast one of the plurality of rectangular patterns which becomes thebasis for a new micro pattern, when the pattern is subdivided into theplurality of rectangular patterns; withdrawing the formation of saidcorrected micro pattern when it is found that there exists a side of atleast one of the plurality of rectangular patterns which becomes thebasis for the new micro pattern; creating a first thickened pattern forthe new micro pattern by increasing the size of the side which served asthe basis for the new micro pattern; creating a second thickened patternby increasing the size of a side of one of said micro patterns adjacentto the new micro pattern; creating a common thickened pattern by takinga logical product of said first and second thickened patterns; creatinganother corrected micro pattern to replace the corrected micro pattern,by combining the common thickened pattern and remaining portions of saidmicro pattern.
 3. The preparation method of an exposure original plateas claimed in claim 2, wherein in the step of correcting the adjacentpattern to form the corrected adjacent pattern, for a case when theredoes not exist a side of any of said plurality of rectangular patternswhich becomes the basis for said micro pattern, the retreated side ofsaid corrected adjacent pattern is extended to an end position in ashort side direction of the adjacent pattern to be given a notch at theend position.
 4. A preparation method of an exposure original platecomprising: subdividing a pattern constituting an exposure originalplate into a plurality of rectangular patterns; extracting at least onemicro pattern having a side smaller than a prescribed size from amongthe plurality of rectangular patterns; forming a corrected micro patternby increasing a size of a side of the extracted micro patternperpendicular to another side of the extracted micro pattern which ismaking contact with an adjacent pattern at least by the prescribed size;finding Electron Beam (EB) exposure data for a pattern including saidcorrected micro pattern and said adjacent pattern, and carry carryingout exposure by a variable shaped exposure method system based on the EBexposure data.
 5. The preparation method of an exposure original plateas claimed in claim 1, wherein said micro pattern is a rectangularpattern with a micro width, which is making contact with adjacentpatterns on both edges in a width direction of said micro pattern, andin the step of forming said correction micro pattern, the micro patternis subjected to a processing of increasing a width size in said widthdirection on both sides of the micro pattern.
 6. The preparation methodof an exposure original plate as claimed in claim 1, wherein said micropattern is a rectangular pattern with a micro width which is makingcontact with an adjacent pattern on one edge of said micro pattern inthe width direction, and in the step of forming said corrected micropattern, the micro pattern is subjected to a processing of increasing awidth size in the width direction on one side of the micro pattern. 7.The preparation method of an exposure original plate as claimed in claim1, wherein said micro pattern is a rectangular pattern with a microwidth and a micro length which is making contact with adjacent patternson edges on both sides in a width direction of said micro pattern, andin the step of forming said corrected micro pattern the micro pattern issubjected to a processing of increasing the size of the micro patterntoward both edges in the width direction and toward both edges in thelength direction of the micro pattern, respectively.
 8. The preparationmethod of an exposure original plate as claimed in claim 1, wherein saidstep of extracting a micro pattern is on the basis of a minimum size atwhich EB exposure by the variable shaped exposure system which performsvariable shaped beam exposure is possible in view of the opticalproximity effect, and extracts a pattern with a size smaller than saidminimum size as a micro pattern.
 9. The preparation method of anexposure original plate as claimed in claim 1, wherein said step offorming the corrected micro pattern is a step of increasing the size ofthe side of said micro pattern to a size of side larger than a minimumsize of said variable shaped beam exposure system that carries out theEB exposure.
 10. The preparation method of an exposure original plate asclaimed in claim 9, wherein said minimum size is 0.1 μm and the size ofthe side of said corrected micro pattern is increased to a size largerthan 0.2 μm.
 11. The preparation method of an exposure original plate asclaimed in claim 1, wherein the pattern constituting said exposureoriginal plate is a pattern to which an optical proximity correction isapplied to a pattern based on design data.
 12. The preparation method ofan exposure plate as claimed in claim 11, wherein said optical proximityeffect correction is at least an optical proximity effect correction bya bias method or an optical proximity effect correlation by an innerserif method.
 13. The preparation method of an exposure original plateas claimed in claim 4, wherein said micro pattern is a rectangularpattern with a micro width, which is making contact with adjacentpatterns on both edges in a width direction of said micro pattern, andin the step of forming said correction micro pattern, the micro patternis subjected to a processing of increasing the size in said widthdirection on both sides of the micro pattern.
 14. The preparation methodof an exposure original plate as claimed in claim 4, wherein said micropattern is a rectangular pattern with a micro width which is makingcontact with an adjacent pattern on one edge in a width direction ofsaid micro pattern, and in the step of forming said corrected micropattern, the micro pattern is subjected to a processing of increasingthe size in the width direction on one side of the micro pattern. 15.The preparation method of an exposure original plate as claimed in claim4, wherein said micro pattern is a rectangular pattern with a microwidth and a micro length which is making contact with adjacent patternson edges on both sides in a width direction of said micro pattern, andin the step of forming said corrected micro pattern, the micro patternis subjected to a processing of increasing the size of the micro patterntoward both edges in the width direction and toward both edges in alength direction of the micro pattern, respectively.
 16. The preparationmethod of an exposure original plate as claimed in claim 4, wherein saidstep of extracting a micro pattern is on the basis of a minimum size atwhich EB exposure by the variable shaped exposure system which performsvariable shaped beam exposure is possible in view of the opticalproximity effect, and extracts a pattern with a size smaller than saidminimum size as a micro pattern.
 17. The preparation method of anexposure original plate as claimed in claim 4, wherein the patternconstituting said exposure original plate is a pattern to which anoptical proximity correction is applied to a pattern based on designdata.
 18. The preparation method of an exposure original plate asclaimed in claim 17, wherein said minimum size is 0.1 μm and the size ofthe side of said corrected micro pattern is increased to a size largerthan 0.2 μm.
 19. The preparation method of an exposure original plate asclaimed in claim 17, wherein said optical proximity effect correction isat least an optical proximity effect correction by a bias method or anoptical proximity effect correction by an inner serif method.